I had back surgery when I was 19 after riding 3-4 days a week for 6 years. I ruptured a disc somehow. I think it's from catching so many back edges at high speeds. Doc said not to ride again. I ended up riding that winter from 1998-2002. Then I ended up casing a 100ft roller. I did a tri-mecular fracture, where you break all 3 bones connecting your ankle to your foot. I needed surgery and was in the hospital for 9 days. Normally they just fuse your foot to your ankle. I had a new doc and he was able to keep some front to back movement. Barely no side to side movement though. Doc said I'll never ride again.
I just bought new stuff and I'm riding again this year at 34 after not riding for 10 years.